The present invention is directed to a dental handpiece which is convertible between an angled handpiece and a straight handpiece. The handpiece has a drive motor part with a drive motor, a housing containing a drive train with at least two drive shaft sections for transferring the rotary motion of the drive motor to a socket in the head part which socket mounts a tool for rotation.
In dental handpieces, one distinguishes between a so called straight handpiece and a so called angled handpiece. In a straight handpiece, the drive shaft sections of the drive train between the drive motor and the tool socket are arranged in axial alignment with each other or with the drive shaft sections being parallel to the axis to the drive shaft of the motor. In an angled handpiece, the drive shaft sections are arranged to be inclined to the drive axis of the motor adjacent the head part with an angle of approximately 18.degree. to 21.degree.. The dentist or physician will require both straight as well as angled handpieces for carrying out preparation work. Since angled handpieces, in particular, are also required with various transmission arrangements to enable a stepping-up in the speed of rotation and also a stepping-down in the speed of rotation, the provision of the desired number of handpiece parts or grip sections involves a relatively high investment for the dentist. If one takes into consideration that the various grip sections or handpiece parts must be frequently connected and disconnected from the drive motor part, these additional handpiece parts with their coupling and uncoupling will increase the wear of the various parts of the entire handpiece. In addition, since it is desirable at the present time to provide a cooling agent at the tool in the socket and for the handpiece to have the cooling lines extend through the drive motor part and grip section or handpiece part with appropriate coupling and sealing arrangement in the vicinity of the coupling of the drive motor part to the remaining handpiece part, the constant removal of the grip sections or handpiece parts from the drive motor will increase the wear of the coupling for the cooling lines with a corresponding increase in the chance of leaking of the cooling fluids.